Thermal relay with two heated bimetallic strips



1970 J. P. ELLENBERGER 3,534,314 I v THERMAL RELAY WITH TWO HEATED .BIMETALIQIC STRIPS Filed Nov. 21. 1966 r 5 Sheets-Sheet 1 FIG. 7.

216 @Lyg 23 INVENTOR JAKOB pmm p ELLENBERGER a! BY v W A? ORNEY} 06L 1970' I J. P. ELLENBERGER 3,534,314

THERMAL RELAY WITH TWO HEATED BIMETALLIC STRIPS Filed Nov. 21,1966 3 Sheets-Sheet 2 JZZH' 0 32 O O O INVENTOR JAKOB PHILIPP ELLENBERGER BY Mr I ATT RNEY Oct 1 9 J. P. ELLENBERGER 3,534,314

THERMAL RELAY WITH TWO HEATED BIMETALLIC STRIPS Filed NOV. 21. 196 6 3 Sheets-Sheet '5 48- FIG 9 U 47 69 70 U 68- & 46 H T I HQ tr :U' 'U 1% 1 FIG. 10.

INVENTOR J AKOB PHILIPP E LLENBERGER BY I AT ORNEY United States Patent US. Cl. 337-96 Claims ABSTRACT OF THE DISCLOSURE A construction of a thermal time-delay relay employes two heated bimetallic strips spaced and mechanically coupled in such a manner as to provide the necessary force. for actuating a microswitch. A variety of thermal compensations and a separate and sequential on and off control of both bimetallic strips accomplished by means of current impulses only, otter a broad field of applications in automatic controls, logical circuits and the like.

The present invention relates to a time-delay relay which is provided with a pair of heated opposite substantially parallel bimetal strips which are spaced from each other for the actuation of switch contacts. More particularly, the invention relates to improvements in a time-delay relay of the above-mentioned type and of a known design in which the two bimetal strips are secured to a block of insulating material and are surrounded by heating coils. The free end of one of the bimetal strips is provided with a double contact which, when the relay is in its resting position, is located loosely between the two arms of a U-shaped contact which is secured to but insulated from the end of the other bimetal strip. If a change occurs in the outside temperature or if under the action of the current flowing through the equal heating coils both bimetal strips are bent simultaneously in the same direction, the double contact of one bimetal strip remains at the center of the U-shaped contact of the other bimetal strip without engaging with the two arms thereof. The surrounding temperature therefore exerts no detrimental influence upon this known timedelay relay. The heating coils of the two bimetal strips may be connected in series with the filaments of light bulbs which are used for illuminating a motor vehicle. If one of the filaments is broken, the circuit of the heating coil of one bimetal strip is interrupted so that the latter cools otf with the result that the contacts of both bimetal strips are connected to each other.

It is an object of the present invention to improve a time-delay relay of the known type as above described and to design it in a manner so as to permit its switch contacts to be switched on as well as ofr by means of current impulses.

For attaining this object, the invention provides that the bimetal strip the free end of which actuates the switch contacts is rigidly connected at its other end to the free end of the second bimetal strip the other end of which is secured in a fixed position. The outside temperature has no more a detrimental influence upon therelay according to the invention than upon the known time-delay relay as previously described. An important feature of the relay according to the invention consists in the possibility of employing. both bimetal strips as operating bimetal strips and of controlling them in such a manner that one bimetal strip is used for switching the relay to the on-position and the other bimetal strip for switching it to the elf-position. Although both bimetal strips may be of the same construction for fully compensating the temperature, they may also be of different constructions so as to attain selectively either an overcompensation or undercompensation of the temperature. The bimetal strips may be heated either directly or indirectly for which both strips may be provided with separate heating coils. The dimensions of these heating coils are dependent upon the electric control impulses.

Another feature of the invention consists in providing the bimetal strip which actuates the switch contacts near its rigidly secured end with a contact which is connected to one end of its heating coil and upon which a contact of a contact spring engages when the other, rigidly mounted bimetal strip is in a cold condition. The contact of the contact spring may be adjust in a manner known as such to its accurate position by means of a setscrew upon which the contact spring engages under an initial tension. When the heating coil of the bimetal strip which actuates the switch contacts is energized by a current impulse of a sufiicient strength, the relay according to the invention will carry out a switching movement in one direction and when the heating coil of the second bimetal strip is energized, the relay will carry out a switching movement in the other direction. The contact which is provided on the actuating bimetal strip and the contact of the contact spring have the effect that the coil of this bimetal strip cannot become effective until the other bimetal strip has cooled 01f. If this other bimetal strip is heated by its heating coil, the switch contacts will be separated which prevents the other bimetal strip also from being energized.

Another feature of the invention consists in connecting the free end of the bimetal strip which actuates the switch contacts to the control lever of a micro-switch by making this end of a bifurcated shape the two arms of which embrace the control lever and thus form a simple and reliable connection of the bimetal strip with the control lever of the microswitch. This microswitch may be provided in a conventional manner in the form of a snap switch so as to prevent the control lever of the microswitch from being automatically reversed by the bi-metal strip when the latter is cooling off. This permits the microswitch to remain in a certin desired position for any length of time. The housing of the microswitch which is slidable within the housing of the relay by being provided with lateral projections which are guided in grooves in the relay housing which extend vertically to the bimetal strip is pressed by at least one spring in the direction of the grooves against a setscrew. When this setscrew is actuated, the microswitch will be adjusted either by or against the action of the spring so that its control lever will in the cold condition be properly connected to the associated bimetal strip.

For attaining an automatic control of the relay according to the invention, one of the ends of each heating coil of both bimetal strips may be connected to each other, while the other end of one heating coil may be connected to one contact of the microswitch and the contact spring to another contact thereof. The bimetal strips which are heated by their heating coils will then automatically switch oif their respective heating coils. This automatic switching on and off of the heating coils will continue until the entire circuit is interrupted.

The time-delay relay according to the invention may be employed, for example, for switching control mechanisms at greater time intervals from one particular condition to another. The switching operation is then produced by time-limited current impulses, the length of which may be equal or different for the two switching operations.

The time-delay relay according to the invention may also be employed as an interval relay which may effect certain switching operations at predetermined time inter- 3 vals. The contact of the contact spring and the corresponding contact of the bimetal strip may then serve for stabilizing the thermal capacities on the bimetal strip and will thereby attain uniform time intervals.

The contact of the contact spring and the associated contact on the corresponding bimetal strip cause a locking of the latter if the operating impulse lasts for a greater length of time or if there is a variation in the current which may be caused, for example, by voltage differences.

In order to facilitate the actuation of the switch contacts and to carry out this actuation more accurately, the two bimetal strips may be pivotably mounted at their ends which are connected to each other. If the bimetal strip is bent which actuates the switch contacts, it will be substantially braced on the fixed pivot point. If the other bimetal strip is bent, the bimetal strip which actuates the microswitch will be pivoted about the pivot point. The actuation of the microswitch will thus be facilitated and the switch contacts will be switched over very accurately.

The two bimetal strips may be connected to each other, for example, by means of a block of insulating material which is pivotably mounted on a stationary bolt. In order to permit the two bimetal strips to be accurately adjusted relative to the switch contacts, the second bimetal strip opposite to the actuating bimetal strip is secured to a setscrew on the end opposite to the insultating block. By actuating this setscrew, it is possible to vary the position of the free end of the actuating bimetal strip relative to the switch contacts and thus to adjust this position very accurately.

Another feature of the invention consists in the provision of a contact spring the contact of which cooperates With an adjustable fixed contact and which is secured to and extends parallel to the actuating bimetal strip the heating coil of which is connected in series with a pair of contacts. Since this contact spring does not project laterally over the two bimetal strips, it is possible to make the switch very narrow in the direction transverse to the bimetal strips.

The wiring of the relay may be considerably simplified by employing bare connecting wires within the relay and by inserting them into bores or grooves in the housing which consists of insulating material. These grooves are preferably provided in the lower side of the housing. The electric connections between the elements of the relay to the connecting terminals thereof may, of course, also be provided by a printed circuit.

The features and advantages of the present invention will become more clearly apparent from the following detailed description thereof which is to be read with reference to the accompanying drawings in which FIG. 1 shows a side view of the time-delay relay according to the invention;

FIG. 2 shows an end view of the relay as seen from the left of FIG. 1;

FIG. 3 shows a cross section which is taken along the line IIIIII of FIG 2;

FIG. 4 shows a top view of FIG. 1;

FIG. 5 shows a cross section of the microswitch according to FIG. 3;

FIG. 6 shows a circuit digram of the two heating coils of the bimetal strips and the microswitch;

FIG. 7 shows a top view of another embodiment of the time-delay relay according to the invention in the open condition;

FIG. 8 shows a cross section which is taken along the line VIII-VIII of FIG. 7;

FIG. 9 shows a bottom view of the relay according to FIG. 8;

FIG. 10 shows a diagrammatic view of the two bimetal strips according to FIG. 7 before and after they are bent; and

FIG. 11 shows a circuit diagram of the time-delay relay as illustrated in FIGS. 7 to 9.

The time-delay relay according to the invention as illustrated in FIGS. 1 to 4 of the drawings comprises a base plate 1 of insulating material which is provided with a projection 2 which is integrally molded thereon. Base plate 1 carries a bimetal strip 4 which is secured thereto at the point 3 and is provided with a heating coil 5, the ends of which are connected to the terminals 6 and 7. As shown in FIG. 1, a block of insulating material 8 is rigidly secured to the left end of the bimetal strip 4. This insulating block 8 may consist of two equal parts which are secured to each other by a screw 9. For holding the bimetal strip 4 and a further bimetal strip 10, both parts of the insulating block 8 are provided with cuts 11 and 12 into which the two bimetal strips 4 and 10 are inserted. The bimetal strip 10 carries a heating coil 13 one end of which is connected to a terminal 14. Adjacent to its end which is secured to the insulating block 8, the bimetal strip 10 is provided with a contact part 15 with a contact 16 thereon which is operatively associated with a contact 17 on one end of a contact spring 18 the other end of which is rigidly secured to a projection 19 on base plate 1. For adjusting the contact 17 of the contact spring 18 relative to contact 16, a setscrew 20 is screwed into the base plate 1 and contact spring 18 engages thereon under tension. Contact spring 18 is electrically connected to a terminal 21. The two bimetal strips 4 and 10 and their heating coils 5 and 13 may be of equal dimensions so as to attain a full temperature compensation of the relay.

The right end of the bimetal strip 10 as shown in FIG. 1 is made of a bifurcated shape so as to form two arms 22 and 23 between which one end of a control level 24 of a microswitch 25 engages. This control lever 24 is pivotally mounted at 26 on the housing 27 of the microswitch 25. As illustrated particularly in FIG. 5, this microswitch is provided with six contact springs 28 to 33. The movable contact springs 29 and 32 are connected at their right ends to an insulating plate 34 which has a central projection 35 which is connected to a similar projection 35 on the control lever 24 by means of a substantially C-shaped tensioned spring 36 which acts as a snap member so that the switching movements of the toggle switch will occur abruptly.

Base plate 1 is further provided underneath the bimetal strip 4 and the insulating block 8 with an aperture 37. The housing 27 of the microswitch 25 is composed of several parts which are secured to each other by pins 38 which project laterally from the housing 27 and the ends of which engage into and are slidable along vertical grooves 39 in the two side walls of a recess 40 in the projection 2 of base plate 1 so as to permit the housing 27 of the microswitch to move in the vertical direction. A spring 41 presses this housing 27 against a setscrew 42 which is screwed into a plate 43 which is secured to the projection 2. This setscrew 42 permits the microswitch 25 to be adjusted within the recess 40 to such a position that, when the relay is in its inactive position, the narrow end 24' of the control lever 24 will engage between the two arms 22 and 23 on the end of the bimetal strip 10.

The mode of operation of the time-delay relay as illustrated in FIGS. 1 to 4 is as follows:

When the bimetal strip 4 is heated by the heating coil 5, it will bend downwardly as shown in FIG. 3. This causes the left end of the bimetal strip 10 to be lifted so that this end will pivot the control lever 24 in the counterclockwise direction, whereby the contacts of the movable contact springs 29 and 32 will engage upon the contacts on the contact springs 30 and 33. Control lever 24 will remain in this position even if the bimetal strip 4 cools off after the current impulse no longer passes through its heating coil 5. For moving the microswitch to the other switching position, a current impulse is passed through the heating coil 13 on the bimetal strip 10 so that the latter bends downwardly and thereby pivots the control lever 24 in the clockwise direction to the other switching position in which the contacts of the movable contact springs 29 and 32 engage upon the contacts of the fixed contact springs 28 and 31.

When the bimetal strip 4 as shown in FIG. 3 bends downwardly as previously described, contact 16 of the contact part of the bimetal strip disengages from the contact 17 on contact spring 18 so that the circuit of the heating coil 13 on the bimetal strip 10 is interrupted. This circuit of heating coil 13 willnot be closed again until the lower bimetal strip 4 has cooled off sufficiently.

As illustrated in the circuit diagram of FIG. 6, the heating coils 5 and 13 are connected at one end at 44 to each other and then to one terminal 45 of a source of current. The other end of heating coil 13 is connected through the contact spring 18 to the contact 33 of the microswitch 25, while the heating coil 5 is connected to the contact 31 of the microswitch 25; If the mentioned circuit is closed, the microswitch 25 will be switched over by the heated bimetal strip 25 so that the contact on contact spring 29 will then engage upon the contact 30 and the contact on contact 32 upon the contact 33. The circuit of heating coil 13 will, however, not be closed by the contacts 16 and 17 until the bimetal strip 4 has cooled off. When these contacts 16 and 17 are closed, the microswitch 25 will again be switched back to the position as shown in FIG. 6. These automatic switching over and back operations will occur until the entire circuit is interrupted. A single switching over and back operation will occur as the result of individual relatively short current impulses.

The time-delay relay as illustrated in FIGS. 7 to 9 comprises a housing 46 of insulating material which has a projection 47 integrally molded thereon and may be covered up by a cover, not shown, which may likewise consist of insulating material and is preferably transparent. For installing the relay, the housing 46 and the projection 47 are each provided with an eye 48 for receiving a bolt.

For the electric connections of the relay, the terminals 49 to 53 are provided on housing 46.

In the bottom of housing 46 a pin 54 is secured on which an insulating block 55 is pivotably mounted. This insulating block 55 may consist of two parts which are provided with cuts 56 and 57 into which the bimetal strips 58 and 59 are inserted. They may be secured to the insulating block 55 by connecting the two halves of the latter to each other by means of screws or by a hollow rivet through which the pin 54 is inserted. The two bimetal strips 58 and 59 carry heating coils 60 and 61 which are electrically insulated therefrom. The left end of the bimetal strip 58 as shown in FIG. 7 is secured to a setscrew 62 on housing 46, preferably by being hooked into an annular groove 63 in setscrew 62. The other bimetal strip 59 is provided with a contact spring 64 which may, for example, be soldered, welded or screwed thereon. On its free end, contact spring 64 carries a contact 65 which in the position as shown in FIG. 7 engages upon an opposite adjustable contact 66. The left end 67 of bimetal strip 59 is bifurcated, and between the two arms of this bifurcated end 67 the free end of the control lever 24 of the microswitch 25 is loosely inserted. This microswitch 25 is provided with six terminal strips 28 to 33. The connecting wires 68 between these terminal strips 28 to 33 or the heating coils 60 and 61 of the two bimetal strips 58 and 59 and the terminal strips 49 to 53 are passed through bores 69 in the bottom of housing 46 and then within grooves 70 in the lower side of this bottom so as to be completely insulated from each other. These connecting wires 68 may therefore be completely bare of any insulation.

The mode of operation of the time-delay relay according to FIGS. 7 to 9 is as follows:

If the heating coil 60 on the bimetal strip 58 is connected to the current, this bimetal strip will bend to the position as indicated by the dotted line 58 in FIG.

10, while the bimetal strip 59 will be pivoted about the 59' and the control lever 24 will thereby be pivoted in the clockwise direction from the position as shown in FIG. 7.

After the bimetal strip '58 has cooled off, it will return to the full-line position as shown in FIG. 10. The control lever 24 will then, however, not be pivoted by the actuating bimetal strip 59 back to the position as shown in FIG. 7, but it will remain in its lowest position to which it was previously pivoted in the clockwise direction.

If the control lever 24 should be pivoted back in the counterclockwise direction to the position according to FIG. 7, the heating coil 61 on bimetal strip 59, the left end of which is electrically connected at 68- to the bimetal strip 59, is connected to the current, whereby the bimetal strip 59 will be pivoted upwardly and take along the control lever v24 which is then pivoted in the counterclockwise direction to the position as shown in FIG. 7. When the bimetal strip 59 has cooled off, the control lever 24 will remain in the position as shown in FIG. 7.

Since both bimetal strips 58' and 59 are bent in the upward direction, one bimetal strip serves for the temperature compensation of the other strip so that the outer temperature will have no influence upon the relay.

When the bimetal strip 58 is bent and the other bimetal strip 59 is thereby pivoted in the counterclockwise direction, contact 65 on contact spring 64 disengages from the opposite fixed contact 66 so that the circuit of heating coil 61 on the bimetal strip 59 will be interrupted. As long as this interruption continues, heating coil 61 cannot be supplied with current and the bimetal strip 59 therefore cannot be bent.

The time-delay relay may be controlled by current impulses of a length greater than that which is required for switching over the bimetal strips. The pair of contacts 65 and 66 prevents the bimetal strip 59 from also being bent by the same current impulse which causes the bimetal strip 58 to bend. Consequently, it is definitely insured that the microswitch 25 cannot be switched back except by a second impulse after the first impulse has been completed.

The circuit diagram as shown in FIG. 11 illustrates that each current impulse which is received by the terminals 52 and 53 will change the microswitch to such a position that the circuit of the heating coil of one bimetal strip will be interrupted and the circuit of the heating coil of the other bimetal strip will be closed. However, the circuit of heating coil 61 of the bimetal strip 59 will not be closed until the two contacts 65 and 66 are also closed.

Although my invention has been illustrated and de scribed with reference to the preferred embodiments thereof, I wish to have it understood that it is in no way limited to the details of such embodiments but is capable of numerous modifications within the scope of the ap pended claims.

Having thus fully disclosed my invention, what I claim 1s:

1. A thermal relay comprising, a support means, first and second bimetallic strips rigidly connected with each other on said support means at their respective first ends in spaced apart parallel relationship, said first strip secured at the second end to said support means, movably mounted switch means operatively loosely connected to the second end of said second strip,

individual coils mounted on each of said strips for heating thereof by individual current impulses,

additional switch means including a first contact on said second bimetallic strip at a point adjacent said first secured end thereof and connected to one end of the heating coil on said second strip, and

a contact spring mounted on said support means having a second contact thereon for engaging said first contact when said first bimetallic strip is in one position,

wherein when one of said strips is heated by one current impulse, the contacts of the additional switch means are connected and when the other of said strips is heated by another current impulse, the switching contacts are disconnected and wherein first and second strips being deflected in the same direction when heated.

2. A relay as defined in claim 1, further comprising a setscrew for adjusting the position of said second contact, said contact spring engaging said setscrew under pressure.

3. A relay as defined in claim 1, in which said firstmentioned switch means comprise a microswitch having a control lever pivotable at one end for actuating said switch contacts, said second end of said second strip being connected to the other end of said control lever for pivoting the same.

4. A relay as defined in claim 3, in which said second end of said second strip is bifurcated so as to have two arms, said other end of said control lever engaging between said arms.

5. A relay as defined in claim 3, in which said microswitch is provided in the form of a snap switch.

6. A relay as defined in claim 3, wherein said support means has grooves therein extending substantially vertically to said strips, said microswitch disposed within a housing and having projections engaging into and guided along said grooves, a setscrew, and a spring under tension acting upon said housing of said microswitch so as to press the same in the direction of said grooves against said setscrew.

7. A relay as defined in claim 1 further comprising means for pivotably mounting said interconnected ends of said two strips, in which said means comprise a stationary pin, and a block of insulating material to which said first ends of said two strips are secured and which is pivotably mounted on said pin.

8. A relay as defined in claim'7, further comprising a setscrew, attached to said support means, said first strip being secured at its second end to said setscrew.

9. A relay as defined in claim 7, wherein said support means has bores and grooves therein, the connecting wires within said relay consisting of bare wires extending separately from each other through said bores and grooves I so as to be insulated from each other.

10. A relay as defined in claim 9, in which said grooves for said bore connecting wires are provided in the lower side of said support means.

References Cited BERNARD A. GILHEANY, Primary Examiner D. M. MORGAN, Assistant Examiner US. Cl. X.R. 337-103, 104, 112 

